Electric and so-called “hybrid-electric” vehicles store electrical power in an electric power storage, such as a battery. The electric power is used by the vehicle to be converted into useful work, such as by powering electric motors that are connected to the vehicle's wheels. In these hybrid-electric vehicles, a combustion engine, such as a petrol or diesel engine rotates an electric generator that produces electric power, is stored in a battery for powering one or more electric motor(s). The electric power in electric and hybrid-electric vehicles may also be generated using other means such as regenerative braking, which converts the energy dissipated during the braking and slowing down of the vehicle into electric energy for example.
The electric vehicle (EV), which lacks an independently fueled engine, relies on an external power source to provide the energy stored in the battery. The electric vehicle therefore includes a charging plug receptacle that allows a vehicle operator to couple the vehicle to a utility-grid connected electric circuit. Electrical power is transferred from the utility-grid connected electric circuit to the vehicle for charging or recharging the batteries. A third type of vehicle, a so-called plug-in hybrid electric (“PHEV”) includes an engine for generating power during operation, but also incorporates a charging plug receptacle to allow recharging the battery when the vehicle is not in use.
In an effort to promote standardization and interoperability, different standards have been proposed, such as the American J1772 standard promoted by the Society of Automotive Engineers (SAE) for example, that establish defined charging plug receptacle and plug parameters and protocols for enabling charging. The J1772 standard provides three different levels of charging. Typically, the charging level depends on the capability of the vehicle to receive electric power and the ability of the utility-grid connected electrical circuit to deliver the power.
Level 1 charging allows the vehicle to receive electric power from a 110 volt, 15-ampere circuit, such as that typically found in a common residential circuit. Level 1 charging provides an advantage in allowing the operator to connect in many locations using standard circuits, such as those commonly found in a residential garage. However, due to the low power capacity of these electrical circuits, an electric vehicle requires 24-26 hours to fully charge.
Level 2 charging allows the vehicle to receive electrical power from a 220V, 30 ampere circuit for example. The Level 2 charging will typically recharge a vehicle battery in three to six hours. These 220V circuits are found in some residences and may be used for certain existing appliances, such as a clothes dryer for example.
Level 3 charging, provides for charging the vehicle using a 440V circuit. The charging of the vehicle on a Level 3 circuit typically allows the charging of the vehicle battery in two to three hours.